Umbraco Mocked Backoffice

Status: This skill is currently awaiting an update from Umbraco to allow external extensions to use the mocked backoffice. The patterns documented here work when running from within the Umbraco-CMS source repository.

Run the full Umbraco backoffice UI with all API calls mocked - no .NET backend required.

When to Use

• Visually test extensions during development
• Rapid iteration without backend deployment
• Test extensions in realistic UI environment
• Demonstrate extensions without infrastructure
• CI/CD testing without backend setup

Related Skills

• umbraco-example-generator - Set up extensions for mocked backoffice (start here)
• umbraco-testing - Master skill for testing overview
• umbraco-unit-testing - Test extension logic in isolation
• umbraco-e2e-testing - Test against a real Umbraco instance

Two Mocking Approaches

Extensions with custom APIs can use two mocking approaches:

Both approaches require MSW to be enabled (VITEUMBRACOUSE_MSW=on) for core Umbraco APIs.

Setup

Create Your Extension

Use the umbraco-example-generator skill to set up your extension:

Invoke: skill: umbraco-example-generator

This covers:

• Cloning Umbraco-CMS repository
• Extension structure and src/index.ts requirements
• Running with VITEEXAMPLEPATH and npm run dev

Add Testing Dependencies

{
  "devDependencies": {
    "@playwright/test": "^1.56"
  },
  "scripts": {
    "test:mock-repo": "playwright test --config=tests/mock-repo/playwright.config.ts",
    "test:msw": "playwright test --config=tests/msw/playwright.config.ts"
  }
}

npm install
npx playwright install chromium

Directory Structure

my-extension/Client/
├── src/
│   ├── index.ts                # Entry point (loads manifests, registers MSW handlers)
│   ├── manifests.ts            # Production manifests
│   ├── feature/
│   │   ├── my-element.ts
│   │   └── types.ts
│   └── msw/                    # MSW handlers (loaded from index.ts)
│       └── handlers.ts
├── tests/
│   ├── mock-repo/              # Mock repository tests
│   │   ├── playwright.config.ts
│   │   ├── my-extension.spec.ts
│   │   └── mock/
│   │       ├── index.ts        # Mock manifests (replaces repository)
│   │       ├── mock-repository.ts
│   │       └── mock-data.ts
│   └── msw/                    # MSW tests
│       ├── playwright.config.ts
│       └── my-extension.spec.ts
├── package.json
└── tsconfig.json

Entry Point (src/index.ts)

The entry point conditionally loads MSW handlers or mock manifests based on environment:

// Entry point for external extension loading
// Run from Umbraco.Web.UI.Client with:
//   VITE_EXAMPLE_PATH=/path/to/extension/Client VITE_UMBRACO_USE_MSW=on npm run dev
//   VITE_EXAMPLE_PATH=/path/to/extension/Client VITE_USE_MOCK_REPO=on VITE_UMBRACO_USE_MSW=on npm run dev

// Register MSW handlers when running in MSW mode (but not mock-repo mode)
if (import.meta.env.VITE_UMBRACO_USE_MSW === 'on' && import.meta.env.VITE_USE_MOCK_REPO !== 'on') {
  import('./msw/handlers.js').then(({ createHandlers }) => {
    const { addMockHandlers } = (window as any).MockServiceWorker;
    addMockHandlers(...createHandlers());
  });
}

// Export manifests - use mock repository if VITE_USE_MOCK_REPO is set
export const manifests = import.meta.env.VITE_USE_MOCK_REPO === 'on'
  ? (await import('../tests/mock-repo/mock/index.js')).manifests
  : (await import('./manifests.js')).manifests;

Running Tests

Self-contained external-example support (automatic)

Loading an extension from a path outside the Umbraco client requires the client to support an absolute VITEEXAMPLEPATH (via Vite's /@fs/) plus a shared-package resolver so @umbraco-cms/backoffice, lit and @umbraco-ui/uui resolve to the client's single copy. Stock released v18 only supports relative (./examples/...) paths.

To stay self-contained, this repo's mocked configs wire a Playwright globalSetup/globalTeardown (plugins/umbraco-testing-skills/harness/mocked-backoffice/) that injects that support into the client at UMBRACOCLIENTPATH before the dev server starts and reverts it afterwards (file-backup based; it detects clients that already have the support and no-ops). So no CMS branch is required — only a built v18 client (npm ci in Umbraco.Web.UI.Client).

First run against a freshly-patched client may re-optimize deps and briefly restart the dev
server (a flaky first navigation); the configs set retries to absorb it. Warm runs are stable.

Environment Variables

Manual Dev Server

cd /path/to/Umbraco-CMS/src/Umbraco.Web.UI.Client

# MSW mode (uses your handlers for custom APIs)
VITE_EXAMPLE_PATH=/path/to/extension/Client VITE_UMBRACO_USE_MSW=on npm run dev

# Mock repository mode (uses mock repository for custom APIs)
VITE_EXAMPLE_PATH=/path/to/extension/Client VITE_USE_MOCK_REPO=on VITE_UMBRACO_USE_MSW=on npm run dev

Run Tests

cd /path/to/extension/Client

# Set path to Umbraco client
export UMBRACO_CLIENT_PATH=/path/to/Umbraco-CMS/src/Umbraco.Web.UI.Client

# Run MSW tests
npm run test:msw

# Run mock repository tests
npm run test:mock-repo

Playwright Config Example

Create tests/msw/playwright.config.ts:

import { defineConfig, devices } from '@playwright/test';
import { fileURLToPath } from 'url';
import { dirname, resolve } from 'path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

const EXTENSION_PATH = resolve(__dirname, '../..');
const UMBRACO_CLIENT_PATH = process.env.UMBRACO_CLIENT_PATH;
if (!UMBRACO_CLIENT_PATH) {
  throw new Error('UMBRACO_CLIENT_PATH environment variable is required');
}

const DEV_SERVER_PORT = 5176;

export default defineConfig({
  testDir: '.',
  testMatch: ['*.spec.ts'],
  timeout: 60000,
  expect: { timeout: 15000 },
  fullyParallel: false,
  workers: 1,

  // Start dev server with extension and MSW enabled
  webServer: {
    command: `VITE_EXAMPLE_PATH=${EXTENSION_PATH} VITE_UMBRACO_USE_MSW=on npm run dev -- --port ${DEV_SERVER_PORT}`,
    cwd: UMBRACO_CLIENT_PATH,
    port: DEV_SERVER_PORT,
    reuseExistingServer: !process.env.CI,
    timeout: 120000,
  },

  use: {
    baseURL: `http://localhost:${DEV_SERVER_PORT}`,
    trace: 'on-first-retry',
    screenshot: 'only-on-failure',
  },
  projects: [
    {
      name: 'chromium',
      use: { ...devices['Desktop Chrome'] },
    },
  ],
});

For mock-repo tests, change the command to include VITEUSEMOCK_REPO=on:

command: `VITE_EXAMPLE_PATH=${EXTENSION_PATH} VITE_USE_MOCK_REPO=on VITE_UMBRACO_USE_MSW=on npm run dev -- --port ${DEV_SERVER_PORT}`,

Test Patterns

Navigation Helper

import { type Page } from '@playwright/test';

async function navigateToSettings(page: Page) {
  await page.goto('/section/settings');
  await page.waitForLoadState('domcontentloaded');
  await page.waitForSelector('umb-section-sidebar', { timeout: 30000 });
}

Testing Tree Items

test('should display root tree items', async ({ page }) => {
  await navigateToSettings(page);

  await page.waitForSelector('umb-tree-item', { timeout: 15000 });
  const treeItems = page.locator('umb-tree-item');
  await expect(treeItems.first()).toBeVisible();
});

test('should expand tree item to show children', async ({ page }) => {
  await navigateToSettings(page);

  const expandableItem = page.locator('umb-tree-item').filter({ hasText: 'Group A' });
  const expandButton = expandableItem.locator('button[aria-label="toggle child items"]');
  await expandButton.click();

  const childItem = page.locator('umb-tree-item').filter({ hasText: 'Child 1' });
  await expect(childItem).toBeVisible({ timeout: 15000 });
});

MSW Mock Document URLs

Troubleshooting

Extension not appearing

• Check that your extension exports a manifests array from src/index.ts
• Check browser console for errors
• Verify VITEEXAMPLEPATH points to the Client directory

Tests timeout waiting for elements

• Ensure the dev server is running with your extension loaded
• Check the browser console for extension loading errors
• Use longer timeouts (15000ms+) for initial element appearance

MSW handlers not intercepting requests

• Check console for [MSW] logs showing handler registration
• Verify handler URL patterns match the actual API calls
• Use browser DevTools Network tab to see actual request URLs

Working Example

See tree-example in umbraco-backoffice-skills/examples/tree-example/Client/:

cd tree-example/Client
export UMBRACO_CLIENT_PATH=/path/to/Umbraco-CMS/src/Umbraco.Web.UI.Client

npm run test:msw        # Run MSW tests
npm run test:mock-repo  # Run mock repository tests

What's Mocked?

MSW provides mock data for all backoffice APIs:

• Documents, media, members
• Document types, media types, member types
• Data types, templates, stylesheets
• Users, user groups, permissions
• Languages, cultures, dictionary items